Zn/HZSM-5正庚烷临氢异构化催化剂研究OA

Objective Isoparaffins are crucial clean blending components for enhancing the octane number of gasoline,but achieving optimal isomerization performance in the isomerization of n-heptane over HZSM-5 zeolite remains challenging.Therefore,it is necessary to introduce active metal Zn to modify HZSM-5 and study the effect of Zn loading on the intrinsic acidic structure of the catalyst,isomerization performance,and regulation of the octane number of the products.Method Zn-modified HZSM-5 bifunctional catalysts with metal-acid centers were prepared by the equal-volume impregnation method.Characterization and investigations were performed using X-ray diffraction,field emission scanning electron microscopy,infrared rheometry,and ammonia programmed temperature desorption.The influence of Zn loading on catalyst structure and n-heptane isomerization performance was investigated,while the product octane number was calculated using the group contribution method.Result The introduction of Zn improved the acidity and activity of HZSM-5,significantly enhancing the catalyst's isomerization performance.As the loading increased,the conversion rate and isomerization selectivity of n-heptane isomerization initially increased and then decreased.Conclusion When the loading was 6%(mass fraction the same below),the support acidity was optimal,promoting the reaction toward maximum isomerization degree.Exceeding 6%loading led to excessive metal coverage of active sites,hindering the reaction.The 6%Zn/ZSM-5 catalyst achieved a n-heptane isomerization conversion rate of 60.04%,an isomerization selectivity of 44.11%,and a product octane number of 44.24,representing a significant improvement over n-heptane(octane number of 0).When applied to naphtha isomerization,the catalyst increased the octane number from 60.70 to 71.20.